Optical code scanners are used in point of sale (POS) terminals to read optical codes on items which are presented to the POS terminals for purchase as part of a purchase transaction. An image based optical code scanner may suitably use multiple image capture devices to capture images of a space above the optical code scanner through which items are passed for scanning. Each captured image is processed to detect and decode any optical code that was captured in the image. Optical code scanners use multiple image capture devices to maximize the area of coverage above the optical code scanner. As an optical code passes through the area of coverage for the optical code scanner, it is possible that multiple image capture devices will capture an image of the optical code and be able to decode it. When a first image capture device fails or experiences degraded performance, other image capture devices will typically still be able to read the optical code. While the ability to still read the optical code helps to maintain the overall performance of the optical code scanner, it masks the fact that an image capture device has failed or is experiencing degraded performance. However at some point, for example when a second or a third image capture device fails or experiences degraded performance, the optical code scanner may suddenly fail or experience a major reduction in performance that causes it to be taken out of service.